Re: [PATCH 12/15] cxl/pci: Add error handler for CXL PCIe port RAS errors

Jonathan Cameron
2024-10-17T13:57:07Z

On Tue, 8 Oct 2024 17:16:54 -0500
Terry Bowman <terry.bowman@amd.com> wrote:

> The CXL drivers do not contain error handlers for CXL PCIe port
> device protocol errors. These are needed in order to handle and log
> RAS protocol errors.
>
> Add CXL PCIe port protocol error handlers to the CXL driver.
>
> Provide access to RAS registers for the specific CXL PCIe port types:
> root port, upstream switch port, and downstream switch port.
>
> Also, register and unregister the CXL PCIe port error handlers with
> the AER service driver using register_cxl_port_err_hndlrs() and
> unregister_cxl_port_err_hndlrs(). Invoke the registration from
> cxl_pci_driver_init() and the unregistration from cxl_pci_driver_exit().
>
> [1] CXL3.1 - 12.2.2 CXL Root Ports, Downstream Switch Ports, and
> Upstream Switch Ports
>
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
A few comments inline.

Jonathan

> ---
> drivers/cxl/core/pci.c | 83 ++++++++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxl.h | 5 +++
> drivers/cxl/pci.c | 8 ++++
> 3 files changed, 96 insertions(+)
>
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index c3c82c051d73..7e3770f7a955 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -815,6 +815,89 @@ static void cxl_disable_rch_root_ints(struct cxl_dport *dport)
> }
> }
>
> +static int match_uport(struct device *dev, const void *data)
> +{
> + struct device *uport_dev = (struct device *)data;
> + struct cxl_port *port;
> +
> + if (!is_cxl_port(dev))
> + return 0;
> +
> + port = to_cxl_port(dev);
> +
> + return port->uport_dev == uport_dev;
> +}
> +
> +static void __iomem *cxl_pci_port_ras(struct pci_dev *pdev)
> +{
> + void __iomem *ras_base;
> + struct cxl_port *port;
> +
> + if (!pdev)
> + return NULL;
Why would this happen? Seems an odd check to have so maybe a comment.

> +
> + if ((pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT) ||
> + (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM)) {
> + struct cxl_dport *dport;
> +
> + port = find_cxl_port(&pdev->dev, &dport);
Can in theory fail.
> + ras_base = dport ? dport->regs.ras : NULL;
> + put_device(&port->dev);
If it fails this is a null pointer dereference.

> + return ras_base;
> + } else if (pci_pcie_type(pdev) == PCI_EXP_TYPE_UPSTREAM) {
> + struct device *port_dev __free(put_device);

Should be combined with the next line. We want it to be hard for anyone
to put code in between!

> +
> + port_dev = bus_find_device(&cxl_bus_type, NULL, &pdev->dev, match_uport);
> + if (!port_dev)
> + return NULL;
> +
> + port = to_cxl_port(port_dev);
> + if (!port)
> + return NULL;
> +
> + ras_base = port ? port->uport_regs.ras : NULL;

Given check above, port exists. Remove one of the two
checks.

> + return ras_base;
> + }
> +
> + return NULL;
> +}